Two-wire party-line lock-out telephone system.



THG. MARTIN.

TWO WIRE PARTY LINE LOCKOUT TELEPHONE SYSTEM.

APPLICATION FILED JAN. 3. 1911- RENEWED APR. 29. I918.

Patented Jan. 14, 1919.

3 SHEETS-SHEET I.

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WITNESSES WTTOR/VEYS,

T. G. MARTIN.

TWO WIRE PARTY LINE LOCKOUT TELEPHONE SYSTEM- APPLICATION FILED 1AN.3.19H. RENEWED APR. 29. 1918.

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TWO WIRE PARTY LINE LOCKOUT TELEPHONE SYSTEM.

APPLICATION FILED IAN.3.19H. RENEWED APR. 29, 1918.

1,291,587. Patented Jan. 14,1919.

3 SHEETS-SHEET 3- IIIHIIIIIIIIIIIII W/ 77VE$5E5 f/VVE/VTOR:

UNITED SATES PATENT OFFICE.

TALBOT G. MARTIN, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TWO-WIRE PARTY-LINE LOCK-OUT TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Jan. 14:, 1919.

Application filed January 3, 1911, Serial No. 600,610. Renewed April 29, 1918. Serial No. 231,539.

To all whom it may concern 7 Be it known that. I, TALBOT G. MARTIN, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful-Improvement in Two-Wire Party-Line Lock- Out Telephone Systems, of which the following is a specification.

My invention relatesto telephone systems in general, but more particularly to lock-out party line systems, and especially to those having provisions for calling automatically or semi-automatically.

My invention relates to party-line systems, for example, in' which the look-out means are controlled by the normal condition of the line to enable the calling subscriber to take the line, and in which this normal condition of the line is changed as soon as the line is taken, in order that some other subscriber on the same line may not interfere with said first subscriber in the use thereof.

Generally stated, therefore, the object of my invention is to provide improved means for enabling a line when once taken to be retained by the subscriber-so taking it, and to enable him also, if he so desires, to send impulses over said line for operating automatic switches or signals.

It is also an object to provide certain details and features of improvement and combinations tending to increase the efiicienoy and serviceability of a telephone exchange system of this particular character. I

To the foregoing and other useful ends my invention consists in matters hereinafter set forth and claimed.

' In the accompanying drawings F1gures l and 2 taken together show a complete circuit connection between a calling substation A (Fig. 1) and a called substation A (F1 2 in a system embodying the principles 0 my invention.

Fig. 3 is a diagrammatic representation of the essential features of theso-oalled master switch D (Fig. 1),

In Fig. 1 there is shown a party-line to which the two telephones A and A are connected. This line is connected with the in dividual or line switch C at the central office. A number of individual switches C are controlled by a common master switch D and similar switches, has common access to a number of groups of trunk lines leading to connector switches F (Fig. 2), which in turn have direct access to the calling terminals of the subscribers lines.

The line switches C and C and master switch D are of the general type disclosed in British Patent No. 26,301 of 1906, and in the American Telephone Journal, of New York, N. Y., of June 6, 1908, having a somewhat modified construction. Referring to the line switch C, the operating winding 2, cut-ofi" winding 3, and line windng 1 are placed upon a single core forming a plural wound electrom'agnet having two distinct magnetic circuits, so that the windings upon one end have no effect upon the arma-tures upon the other end. Of the windingsupon the upper end of the magnet the winding 2 1s strong enough to operate both the plunger arm 12 and eut-ofi' armature 5, while the winding 3,;though strong enough to operate the armature 5 and to hold the plunger arm 12 in its operated position, is not strong plunger arm from its Filifltiou Wire system, 2'. e., a system in which the central ofiice apparatus is controlled by im pulses transmitted from the calling substation over the two sides of the line in series. The release magnet 105 is preferably arranged to release the switch mechanism immediately upon energizing in the manner shown in United States Letters Patent No. 815,176 for connector switches, rather than upon deenergizing as shown in said selector Patent No. 815,321. The relays 14A, 51 and 38 de'nergize slowly when their energizing circuits are broken. I The connector F is of the general type disclosed in United States Letters Patent No. 815,176, issued March 13, 1906, to Keith, Erickson and Erickson, but, like the selector, ismodified to operate in a two-wire system. The substations may be of any suitable common battery two-wire automatic type. The ones with which I have elected t9 'i'lustrate my invention comprise the usual receiver 6 (see substation A, Fig. 1), switch hook 7, transmitter 8 and ringer 9. For the purpose of producing impulses for controlling the central ofiice apparatus, this substation is also provided with a pair of impulse springs 10 and 11, impulse wheel 18 and a dial (not shown). A pair of springs 8 and 9 are provided for closing a shunt circuit about the transmitter and receiver. In the preferred-form of my invention I provide each substation with a relay which is adapted, when in an operated position, to-

close the contact between the springs 14 and 15, thereby bridging the talking circuit across the line conductors. The relay is also provided with a spring 19 which, when the relay is energized, catches and locks the armature 20 in its operated position until the receiver hook is pulled down. Since the relay, when energized, is locked up mechanically it cannot beaifected by any change in the circuit conditions of the telephone, such as the opening of the line for the purpose of transmitting impulses to the central office. One terminal of thewinding of the relay 13 is connected to the conductor 16, while the other terminal is connected to the hook switch spring 21 which normally engages the spring 22. As the switch hook rises when the receiver is removed, the spring 23 which is connected to the line conductor 17 engages the spring 22 and forces it out of engagement with the spring 21. Thus, for an instant during the upward movement of the switch hook all these springs 21, 22 and 23 are in contact, thereby momentarily bridging the relay 13 across the line. The relay 13 is so wound and adjusted that when it is thus bridged across the line it receives sufficient current from the central office to be operatively energized. If, however, the

talking circuit of some other telephone is in bridge of the line at the time the circuit of the relay 13 is closed, suflicient current is shunted away from the relay by said talking circuit to prevent the relay from being operated. It will be understood that the relay 13 may have any suitable resistance, so as to secure its proper operation. Since the brldging of the talking circuit at a telephone across the line is dependent upon the operation of the relay 13 at that telephone, it will be seen that it will be impossible for a see 0nd subscriber to come in on the line while some other subscriber is using it.- In case one subscriber wishes to call another subscriber on the same line, the first subscriber can, by pressing the button 25 and removing the short-circuit-from the resistance 26, increase the resistance of his talking circuit sufficiently at the time the second subscriber removes his receiver to permit the relay 13 at the second substation to be energized and placethe second telephone in talking condition.

In order to notify a calling subscriber whether or not the line was busy when he mares? attempted to make a call, I provide an opening in the wall of the telephone. Upon the end of the arm 28 of the receiver hook there 1s placed a small target or signal, which may have the word busy written on it. When the receiver hook rises this target comes behind the opening 27 and may 'be seen by the subscriber. To the armature 20 there is attached an arm 29 carrying a shield 30 which, when the relay is energized, 'comes behind the opening 27, but in front of the target on the switch hook arm 28, thereby hldlng said target from the calling subscriber.

The operations by which one subscriber calls another in the system shown herein are as follows: It will be assumed, first, that the subscriber at substation A calls subscriber A No. 220. When the subscriber at substation A removes his receiver a momentary circuit is closed from ground G through the springs 31 and 32, line 17, springs 23, 22 and 21, relay 13, line 16, springs 33 and 34 and winding 4 to the battery lead 35, thence to battery B and to ground. The relay 13 is energized by this impulse and locks up, bridging the talking circuit across the line. The winding 4 of the switch C, upon energizing, attracts the armature 36, which closes the circuit of the winding 2. This circuit extends from ground G through the springs 31 and 110,

operates to force the line switch plunger into a bank of contact springs 113, 114, 45, 44, 115, 116, 117 and 118, forcing them into contact in pairs as shown in the drawings. The armature 5, upon operating, disconnects the line winding 4 and ground G from the calling line, whereupon the armature 36 falls back and opens the circuit of the winding 2. Before the winding 2 is deenergized, however, a circuit is closed through the winding 3 in the following manner: When the springs 113 and 117 are forced into contact with the springs 114 and 118 by the plunger of the line switch C, the line circuit is extended to the first selector switch E, and a circuit is closed from the ground Gr through the lower winding of the relay 37 at the selector E, side switch wiper 119, springs 118 and 117, line 17, talking circuit of the substation A, line 16, springs 113 and 114, side switch wiper 120 and the upper winding of the relay 37 .to battery. The line relay'37 of the selector thereupon energizes and closes the circuit of the slowacting relay 38. This relay 38, upon energizing, completes a circuit from ground Gr through the springs 40, 41, 42, 43, 44 and 45 and winding 3 of the switch C to battery. The winding 3 holds the switch C n its operated position after the armature 36 has fallen back and broken the circuit of the winding 2. In order to insure against the armature 36 falling back before the winding 3 is energized, the auxiliary winding 111-is energized in series with the pull-down winding 2 and is short-circuited through the springs 121 and 122 when the plunger arm reaches the limit of its downward movement. .The winding 111 thus serves to hold up the armature 36 for an instant'afterthe winding 4 is denergized, so as'to give the winding 3 a little longer time in whlch to energize. When the line switch 0 operates, the master switch D operates in a well-known manner to advance the plungers of the idle line switches to an idle trunk.

The operation of the master. switch D is as follows: The closure of contact between the springs 115 and 116 of the line switch C completes a circuit from ground G through the springs 115 and 116, contact point 123 (which is assumed to correspond to the trunk seized by the switch C), wiper 124, segment 165 and relay 125 to battery. The relay 125, upon energizing, closes a circuit through the relay 126. The relay 126, upon energizing, withdraws the pin 12'? from an opening in the locking plate 128 and closes a circuit through the motor magnet 129. This circuit extends fwm ground G through the magnet 129, interrupter springs 130, contact point 131 and armature 132 to battery.' The magnet 129 operates in a manner similar to that of a buzzer as long-as the armature 132 engages the contact point 131, and, through the medium of the ratchet wheel 133 and link 134 (Fig. 3), rotates the plunger shaft 135 about the shaft 136 to move the plungers of the idle line switches to an idle trunk line. As soon as the wiper 124, which moves with the plunger shaft, passes ofi the contact 123, the relay 125 deenergizes and breaks the circuit of the relay 126. The master switch continues to operate, however, until the next opening in the plate 128 passes directly under the pin 127, whereupon the armature 132 falls back and breaks the circuit of the magnet 129. The openings in the plate are so spaced that the armature 132 can fall back only when the plungers of the line switches are directly in front of a trunk line. If busy trunk lines have to be passed before the plungers can arrive at an idle trunk, the relays 125 and 126, are maintained energized by ground potentials on the master switch bank contacts of said busy trunks until the idle trunk is reached.

The calling subscriber now operates his calling device for the first digit 2 of the.

number desired, whereby the impulse springs 10 and 11 which are included in the bridge at the substation are separated twice momentarily, each time opening the line or inserting a high resistance therein and therein causing the line relay 37 of the selector E to be deenergized. In order to eliminate the resistance of the transmitter and receiver from the line circuit, the short-circuit through the springs 8 and 9 is closed at this time. This short-circuit can be closed in any desired manner, but is preferably placed under the control of the calling device, so that when the calling device is operated, the springs 8 and 9 are brought into contact to close this short-circuit. The relay 37, upon -de'6nergizing, closes a circuit from ground G through the springs 46, 48, 49 and 50 (the slow-acting relay 38 does not fall during the momentary interruption of its circuit), relay 51, vertical magnet 52 and side switch wiper 53 to battery. The vertical magnet operates to raise the switch shaft two steps, while the slow-acting relay 51 operates to close the circuit of the private magnet 54. The relay 51 does not have time to denergize until after the last impulse for the digit is delivered, when it then breaks the circuit of the magnet 54, which allows the side switch to pass to second position. The rotary magnet 55 thereupon operates in a well known-manner to rotate the wipers onto an idle trunk leading to a connector F. after which the side switch of the selector passes to third position, cutting ofl the line relay of the selector and extending the line to the line relays 56 and 57 of the connector, whereupon said relays become energized. The energizing circuit for these relays extends from ground Gr through the relay 57, trunk conductor 137, thence over the heavy conductors through the selector E, line switch C, substation A and back over the to battery. The relay 57 of the connector,

upon energizing, completes a circuit from ground Gr through the springs 58 and 59,

60 and 61 andrelay 62 to battery. The relay 62, upon energizing, extends a connec-' tion from ground Gr throughthe side switch wiper 63 and springs 64 and 65 to the conductor 66, for the purpose of providing a guarding potential for the selector private bank contacts of the sized'trunk, and for maintaining a holding circuit for the relay 38 of the selector E. This holding circuit extends from ground G through the side switch wiper 63, springs 64 and 65, conductor 66, private bank contact and wiper 140, side switch wiper 141, springs 1'43 and 142 and relay 38 to battery. The relay 144 of the selector E is energized in series with the rotary ma et, and, being slow acting, remains in its operated position for an instant after the side switch passes to third position, and through the medium of the I the above-described holding circuit before the latter relay drops back.

When the calling subscriber operates his calling device for the second digit 2, the line is again opened twice, each time breaking the circuit of the relays 56 and 57 at the selector. The slow relay 62 does not have.

time to fall back during the momentary 1nterruption of its circuit by the relay 57 consquently, each time the relay 56 deenergizes, a circuit is closed from ground G through the springs 67, 68, 69 and 70, relay 71, vertical magnet 72 and side switch wiper 73' to battery. The magnet 72 operates to raise the shaft and wipers two steps, while the slow acting relay 71 acts in the same manner as explained for the relay 51 of the selector E to cause the privatemagnet 74 to trip the side switch to second position. In passing from first to second position, the side switch wiper 73 transfers the battery connection from the vertical magnet to the rotary, magnet 7 5. When the calling device is operated for the last digit 0 the rotary magnet receives ten impulses and rotates the wipers ten steps onto-the contacts of the line #220, after which the side switch is tripped to third position'by the private magnet in the same manner in which it was tripped to second position after the completion of the impulses for the first digit. The operating circuit of the rotary magnet 75 extends from ground G through the springs 67 and 68, 69 and 70, relay 71, springs 146 and 147, magnet 75 and side switch wiper 73 to battery. When the side switch reaches third position the connection between the calling and the called lines is completed, the called line is provided with a uarding potential at the connector private ank contacts, the line switch 0 is out OK and a circuit is closed through the ringing relay 76. The switch G is out OK by the winding 77,which is energized over a circuit extending from ground G through the side switch wlper 78, private wiper 7 9 and winding 77 to battery. The energizing circuit of the relay 76 extends from ground G through the interrupter 80, springs 81 and 82, relay 76 and side switch'wiper 73 to battery. The relay 76 is energized intermittently to ring the called subscriber. The ringing circuit extends from one terminal of the ringing current generator N through the springs 148 and 149, side switch wiper 150, shaft wiper 151, line 152, substation springs 153 and 154, ringer 155, line 156, springs 157 and 158, wiper 159 and s rings 160 and 161 to the other terminal 0 the generator. When the receiver at the called substation is removed, that substation is provided with talking current through the back-bridge relay 83 of the connector. This circuit over which the talking current is supplied extends from ground Gr through the side switch wiper 78, lower winding of the relay 83, ringing relay springs 162 and 149, thence over the heavy conductors to and through the substation A and back over the other side of the line, and through the ringing relay springs 160 and 163, 164 and 165, upper winding of the relay 83 and side switch Wiper 73 to battery. The relay 83, upon energizing, closes a circuit from ground Cr through the springs 67 and 84 of the relay 56, springs 85 and 86, relay 87 and side switchwiper 73 to battery. The relay 87, upon energizing, breaks the operating circuit of the relay 76 and closes a locking circuit for itself through the springs 88.

The two connected, subscribers may now carry on an uninterrupted conversation, and.

no other subscriber on either line can break in on the connection. Referring to Fig. 1,

suppose the receiver at substation A" is re- 'moved. As the hook goes up a circuitwill be closed through the relay 13 at that sta- 'tion, but said relay will be shunted by the talking circuit at the substation A and will not be operated, thereby leaving the talking circuit open, as shown in Fig. .1.

In case the called line had been busy when the connector F sought to make connection therewith, the private wiper 79 would have found its private bank contact grounded and immediately upon engaging said contact would have extended a ground potential through the sideswitch wiper 78 (in second position), springs 89 and 90 and lower winding of the relay91 to the spring 92. of the private magnet relay 71. As the relay 71' relay 57. The side switch being locked in second position, no connection would be completed with the busy line, and the busy signaling machine M would be connected with the calling line by the closure of the springs 95 at the relay 91.

. From the foregoing it is evident that the connector cannot make connection with a line which has a ground upon its connector private bank contacts. It will also be seen that as soon as the connection is extended to the selector E a guarding potential is extended from groundv G through the springs 40, 41,

V 42, 43, 44 and 45, and over the conductor 96 the calling line.

to the connector private bank contacts of the calling line. In order to permit a subscriber to call back on his own line to signal another subscriber thereon, each trunk line leading to a selector E is provided with the relays 97 and 98, which so modify the guarding potential of the calling line while the calling device at the calling station is being operated as to allow a connector to make connection therewith at that time. It will be seen that all impulses must pass through the relay 97 which, upon de'energizing after connection is extended to the selector E,

closes a circuit through the slow-acting relay 98. The relay 98, upon energizing, removes the short-circuit around the resistance 99,

thereby inserting this resistance in the ground connection to the private contacts of Thus it will be seen that when the calling subscriber is calling back on hisown line, at the time the private magnet relay 71 de'energized after the last digit is called, the resistance 99 will be included in the circuit, which tends to lock the private magnet. This resistance is high enough to prevent. said magnet from being locked, and the side switch passes to third position in the usual manner. A moment later the relay 98 (Fig. 1) falls back and cuts out the resistance 99 to restore the guarding potential of the calling line to its eifective condition.

When a calling subscriber calls back on his own line a circuit will be closed through the back-brid e relay of the connector and the calling su station, which will cause the V circuit'of the ringer relay 76 to be opened.

In order to signal the called substation the calling subscriber must press the button 25,

thereby increasing the resistance of the bridge sufiiciently to allow the connector line relay 56 to fall back, but not the relay 57. The relay 56, upon falling back, breaks the circuit of the relay 87, which falls back and closes the circuit of the ringer relay. The pressing of the button 25 also increases the resistance of the bridge at substation A sufliciently to allow the relay 13 at the called substation to be energized when the called subscriber answers. The bridging of the called telephone across the line causes the relay 56 to again pull up, which causes the ringing current to be cut off. The calling subscriber then releases his button.

After a connection is completed the switches are released by the hanging up of the receiver at the calling substation. This allows the connector line relays to fall back, which removes the holding ground from the release relays 62 and 38' of the switches F and E, respectively. The relay 62, upon deenergizing, completes the circuit of the re lease magnet 101, which releases the connector. The circuit of the magnet 101 is broken at the springs 102 and 103 when the When the relay 38 denergizes-it also breaks the holding circuit of the winding 3 of the switch C, allowing its plunger to be restored.

In party-line systems of the kind shown herein, the different parties on a line may be signaled selectively in the following wellown manner: The bells of the different substations may" be tuned or otherwise adapted to respond to only a certain kind of ringing current. Each subscribers line may be accessible by a plurality of groups of connectors, each group representing a different hundreds digit. The numbers of the diiferent substations on the same line may then be given difi'erent hundreds digits, corresponding to the respective hundreds groups of connectors. Each group of connectors may be supplied with ringing current of the proper character to operate only the ringers of the'su'bstations whose hundreds digits correspond to that connector group. Thus, to signal any particular substation on a. line the line must be called through a connector in a group which is supplled with ringing current of the proper character to operate the bells at the desired substation, and the connector group is determined by the hundreds digit of the called substation.

Throughout this specification, where a telephone is spoken of as being in normal position, it is meant that the receiver is on the switch hook. A line is spoken of as being in normal position when the receivers of all telephones on said line are on their switch hooks.

What I claim as my invention is 1. In a telephone system, a party-line having a plurality of telephone stations thereon, a relay at each of said stations, means for only momentarily energizing said relay when said line is taken for use at any station, means outside the central station controlled by said relay for preventing any other subscriber from coming in on said line when said line is busy, a calling device for said party line, and a progressively movable switch associated with said line, said switch responsive to the operation of the calling ilevice for extending connection to the called 2. In a telephone system, a party-line having a plurality of substations thereon, a relay at each of said substations, means for only momentarily energizing the corresponding relay when a receiver is removed from the hook at a substation, means for locking said relay in energized position, means outside the central station controlled by the energization of said relay for preventing any other subscriber from coming in on said linewhile the same is in use, a calling device for said party line, and a progressively movable switch associated With said line, said switch responsive to the op eration of the calling device for extending connection to the called line.

3. In a telephone system, a party-line having a plurality of subscribers stations thereon, a relay bridged across the lineat each of said stations, means for only momentarily energizing one of said relays upon the removal of the corresponding receiver from its hook, means controlled by said relay for closing the talking circuit, means outside the central station for preventing said relay from energizing when a receiver is re moved from the hook and said line is busy, a calling device for said party line, and a progressively movable switch associated with said line, said switch. responsive to the operation of the calling device for extendingconnection to the called line.

4. In a telephone system, a party-line having a plurality ofsubstations thereon, a relay at each substation bridged across said line, means for only momentarily energizing one of said relays upon removing a receiver from its hook, means for locking said relay in energized position, means outside the central station operated by said relay for closing a low resistance talking bridge across said line in shunt of said relay, said shunt preventing any other relay being energized upon the removal of any other subscribers receiver from the hook, a calling device for said party line, and a progressively movable switch associated with said line, said switch responsive to the operation of the calling device for extending connection to the called line.

5. In a telephone system, a party-line having a plurality of substations thereon, an automatic trunking switch for said line, a relay at each substation bridged across said line, means for only momentarily energizing one of said relays'upon removing a'receiver from its hook, said automatic switch also responsive to the raising'of the switch hook to perform a trunking operation, means for locking said relay in energized position, means operated by said relay for closing a low resistance talking bridge across said line in shunt of said relay, said shunt preventing any other relay being energized upon the removal of any other subscribers receiver from the hook, means for afl'ecting said shunt to thereby permit a second subscriber to come in upon the line, and for preventing the release of the automatic switch while the shunt is so affected.

Signed by me at Chicago, Cook county, Illinois, this 30th day of December, 1910.

TALBOT G. MARTIN,

Witnesses J. Nonnr, S. Lnwis. 

